potting compound removal

[Robert Morein]

A small high frequency transformer in the monitor HV section of a Lecroy
scope has failed.

This part is difficult or impossible to obtain.

It is potted inside a plastic box, which forms a tray. The underside, where
the leads come out, is the potting compound, which has a crack down the
center, perhaps due to the heat.

I would like to de-pot this transformer to study the damage.

I've heard that pineapple juice is the standard solution for removing
potting compound.

Any comments or suggestions?

 

[Marko]

A small high frequency transformer in the monitor HV section of a Lecroy
scope has failed.

This part is difficult or impossible to obtain.

It is potted inside a plastic box, which forms a tray. The underside, where
the leads come out, is the potting compound, which has a crack down the
center, perhaps due to the heat.

I would like to de-pot this transformer to study the damage.

I've heard that pineapple juice is the standard solution for removing
potting compound.

Any comments or suggestions?

Robert, I was told that if the unit is old enough that it may dissolve in
solvent. Try varsol or mineral spirits, they probably won't dissolve the
enamel on the wires. As I understand it, in the 30s 40s and possibly into
the 50s and 60s they used coal tar or something like that.

In later years I think they started using some rubbery type stuff.

Faster thinners like MEK or xylene will probably dissolve it , but they
might also dissolve the enamel, and also your nervous system.

Never heard about pineapple juice. If it is the acidity then vinegar may
also work.

If you figure it out, please post your results. Mark

 

[Robert Morein]

Robert, I was told that if the unit is old enough that it may dissolve in
solvent. Try varsol or mineral spirits, they probably won't dissolve the
enamel on the wires. As I understand it, in the 30s 40s and possibly into
the 50s and 60s they used coal tar or something like that.

In later years I think they started using some rubbery type stuff.

Faster thinners like MEK or xylene will probably dissolve it , but they
might also dissolve the enamel, and also your nervous system.

Never heard about pineapple juice. If it is the acidity then vinegar may
also work.

If you figure it out, please post your results. Mark

This part was made 1989. It's from a digital scope .
The potting material is hard and shiny, possibly a form of two component
acrylic.

 

[Jim Adney]

A small high frequency transformer in the monitor HV section of a Lecroy
scope has failed.

It is potted inside a plastic box, which forms a tray. The underside, where
the leads come out, is the potting compound, which has a crack down the
center, perhaps due to the heat.

I would like to de-pot this transformer to study the damage.

If the potting is soft you may just be able to dig it out. If you have
the hard stuff, then you could try various solvents to see if any of
them would soften it. I've had some luck with acetone, but I had to
leave it soaking overnight, dig out the softened portion and then
repeat. This can take many days, but is workable if you have the time.

I've heard that pineapple juice is the standard solution for removing
potting compound.

I've never heard of this and it doesn't sound reasonable to me. The
only thing in the juice would be a mild acid which shouldn't do
anything to the potting compound, but it might eventually damage metal
parts that were in there.

-

 

[Peter Gottlieb]

This part was made 1989. It's from a digital scope .
The potting material is hard and shiny, possibly a form of two component
acrylic.

Try De-Solv-It which you can find at better hardware stores or Eposolve,
which is very dangerous and available from industrial suppliers such as
McMaster-Carr.

 

[James Sweet]

This part was made 1989. It's from a digital scope .
The potting material is hard and shiny, possibly a form of two component
acrylic.

That's epoxy, good luck dissolving it, anything that will remove it will
likely destroy anything inside it.

 

[Nigel Cook]

A small high frequency transformer in the monitor HV section of a Lecroy
scope has failed.

This part is difficult or impossible to obtain.

It is potted inside a plastic box, which forms a tray. The underside, where
the leads come out, is the potting compound, which has a crack down the
center, perhaps due to the heat.

I would like to de-pot this transformer to study the damage.

I've heard that pineapple juice is the standard solution for removing
potting compound.

Any comments or suggestions?

In a similar circumstance faced with black ,hard, probably
epoxy potting I used a ball mill in a dremmel. Like a rotary
burr but instead of a cylinder on a mandrel it is a small sphere
of burr/file form a few mm in diameter. Cutting
in section by section ,then breaking each section away.
Leaving the external pinning area to last.,counted turns off
and other features (wiring sense,interlayer paper etc)and rewound.
Before starting to break apart make a plan of the
pinning and do a grid plot of all combinations of inter-pin DC resistance
and AC inductance measurements as you are
bound to cut some wires in the process. Mark any cut ends
with indelible felt tip pen marks - good luck.
Time consuming but as
the replacement cost I was quoted was a totally
ridiculous 700 GBP ( 1000 dollars ) for a potted
box less than 2 inch cube ,well worth trying

e-mail (removing .....) [email protected].....k
electronic hints and repair briefs , schematics/manuals list on
http://homepages.tcp.co.uk/~diverse

Nigel,Diverse Devices,Southampton,England

 

[Len]

Back in the says of videocypher 2 sat board hacking they used to use a
heat gun with a concentrator on it, heat up a small spot and use a small
screwdriver to dig it out. Its a real bitch to do but I have seen
people totally remove the stuff and leave all the traces and parts
intact.

That's epoxy, good luck dissolving it, anything that will remove it will
likely destroy anything inside it.

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